Well I don't hybridize but I read an awful lot and can tell you about two that I read about. Drama Queen fertile both ways and Fanta Streaks a white flower with variegated foliage. Blue J says that 33% of it's seedlings are variegated. I collect variegated plants and collect every Iris (especially bearded) that are variegated.

Rena'

I don't hybridize either.
The reason it is hard to answer your question is that it all depends on what your hybridizing goal is. Do you want to try to get rebloomers? A true red iris? A strong-growing black iris with a white beard? The ruffliest iris ever?

Once you have determined a goal, you can begin to choose irises that have the genetic background to give you a better chance to get what you want.

Nice patterns and colors have come out of a number of irises that are not necessarily spectacular award winners. I believe that Wild Jasmine is very popular with hybridizers. Ring Around Rosie produced some beautiful results. You can see the parentage of irises you like on the AIS Iris Encyclopedia.

Take a look at the American Iris Society Blog. Lots of hybridizers talk about what they are up to and how to hybridize there. There's a post right now about it.

Here is a link that might be useful: Iris Blog

Thanks for telling me about the AIS Iris Encyclopedia. Had not yet run across that link.